Growth factors, stem cells, and stroke

Routes and methods of neural stem cells injection in cerebral ischemia

Cerebral ischemia is a serious cerebrovascular disease with the characteristics of high morbidity, disability, and mortality. Currently, stem cell therapy has been extensively applied to a wide range of diseases, including neurological disorders, autoimmune deficits, and other diseases. Transplantation therapy with neural stem cells (NSCs) is a very promising treatment method, which not only has anti-inflammatory, antiapoptotic, promoting angiogenesis, and neurogenesis effects, but also can improve some side effects related to thrombolytic therapy. NSCs treatment could exert protective effects in alleviating cerebral ischemia-induced brain damage and neurological dysfunctions. However, the different injection routes and doses of NSCs determine diverse therapeutic efficacy. This review mainly summarizes the various injection methods and injection effects of NSCs in cerebral ischemia, as well as proposes the existing problems and prospects of NSCs transplantation.

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Galectin-3 protects against ischemic stroke by promoting neuro-angiogenesis via apoptosis inhibition and Akt/Caspase regulation

Post-stroke neurological deficits and mortality are often associated with vascular disruption and neuronal apoptosis. Galectin-3 (Gal3) is a potent pro-survival and angiogenic factor. However, little is known about its protective role in the cerebral ischemia/reperfusion (I/R) injury. We have previously shown significant up-regulation of Gal3 in the post-stroke rat brain, and that blocking of Gal3 with neutralizing antibody decreases the cerebral blood vessel density. Our current study demonstrates that intracerebral local delivery of the Gal3 into rat brain at the time of reperfusion exerts neuroprotection. Ischemic lesion volume and neuronal cell death were significantly reduced as compared with the vehicle-treated MCAO rat brains. Gal3 increased vessel density and neuronal survival after I/R in rat brains. Importantly, Gal3-treated groups showed significant improvement in motor and sensory functional recovery. Gal3 increased neuronal cell viability under in vitro oxygen-glucose deprivation conditions in association with increased phosphorylated-Akt, decreased phosphorylated-ERK1/2, and reduced caspase-3 activity. Gene expression analysis showed down regulation of pro-apoptotic and inflammatory genes including Fas-ligand, and upregulation of pro-survival and pro-angiogenic genes including Bcl-2, PECAM, and occludin. These results indicate a key role for Gal3 in neuro-vascular protection and functional recovery following ischemic stroke through modulation of angiogenic and apoptotic pathways.

L-lactate induces neurogenesis in the mouse ventricular-subventricular zone via the lactate receptor HCA1

AIM

Adult neurogenesis occurs in two major niches in the brain: the subgranular zone of the hippocampal formation and the ventricular-subventricular zone. Neurogenesis in both niches is reduced in ageing and neurological disease involving dementia. Exercise can rescue memory by enhancing hippocampal neurogenesis, but whether exercise affects adult neurogenesis in the ventricular-subventricular zone remains unresolved. Previously, we reported that exercise induces angiogenesis through activation of the lactate receptor HCA1. The aim of the present study is to investigate HCA₁ -dependent effects on neurogenesis in the two main neurogenic niches.

METHODS

Wild-type and HCA₁ knock-out mice received high intensity interval exercise, subcutaneous injections of L-lactate, or saline injections, five days per week for seven weeks. Well-established markers for proliferating cells (Ki-67) and immature neurons (doublecortin), were used to investigate neurogenesis in the subgranular zone and the ventricular-subventricular zone.

RESULTS

We demonstrated that neurogenesis in the ventricular-subventricular zone is enhanced by HCA₁ activation: Treatment with exercise or lactate resulted in increased neurogenesis in wild-type, but not in HCA₁ knock-out mice. In the subgranular zone, neurogenesis was induced by exercise in both genotypes, but unaffected by lactate treatment.

CONCLUSION

Our study demonstrates that neurogenesis in the two main neurogenic niches in the brain is regulated differently: Neurogenesis in both niches was induced by exercise, but only in the ventricular-subventricular zone was neurogenesis induced by lactate through HCA₁ activation. This opens for a role of HCA₁ in the physiological control of neurogenesis, and potentially in counteracting age-related cognitive decline.

CREB controls cortical circuit plasticity and functional recovery after stroke

Treatments that stimulate neuronal excitability enhance motor performance after stroke. cAMP-response-element binding protein (CREB) is a transcription factor that plays a key role in neuronal excitability. Increasing the levels of CREB with a viral vector in a small pool of motor neurons enhances motor recovery after stroke, while blocking CREB signaling prevents stroke recovery. Silencing CREB-transfected neurons in the peri-infarct region with the hM4Di-DREADD blocks motor recovery. Reversing this inhibition allows recovery to continue, demonstrating that by manipulating the activity of CREB-transfected neurons it is possible to turn off and on stroke recovery. CREB transfection enhances remapping of injured somatosensory and motor circuits, and induces the formation of new connections within these circuits. CREB is a central molecular node in the circuit responses after stroke that lead to recovery from motor deficits.

Increasing excitability in the peri-infarct area enhances motor recovery after stroke. Here the authors show that expressing CREB, a transcription factor known for its role in synaptic plasticity, or increasing activity of CREB-expressing cells near the stroke site improves recovery in an effect that is strong enough that it can be used to turn on and off motor recovery after stroke.

Basic Fibroblast Growth Factor Protects Astrocytes Against Ischemia/Reperfusion Injury by Upregulating the Caveolin-1/VEGF Signaling Pathway

A previous in vivo study demonstrated that intracerebroventricular injection of basic fibroblast growth factor (bFGF) in middle cerebral artery occlusion rats increased the expression of caveolin-1 (cav-1) and vascular endothelial growth factor (VEGF) in cerebral ischemia penumbra. Because astrocytes are the largest population in the brain, the aim of this in vitro study was to investigate the influence of bFGF on cav-1 and VEGF expression in rat astrocytes following oxygen glucose deprivation/reoxygenation (OGD/R). For this, an ischemic model in vitro of oxygen glucose deprivation lasting for 6 h, followed by 24 h of reoxygenation was used. Primary astrocytes from newborn rats were pre-treated with siRNA targeting bFGF before OGD/R. Cell viability was measured by a CCK-8 assay. The protein and mRNA expressions of bFGF, cav-1, and VEGF were evaluated by western blotting, immunofluorescence staining, and reverse transcription-quantitative polymerase chain reaction. The results showed that OGD/R reduced cell viability, which was decreased further following bFGF knockdown; however, restoring bFGF improved cell survival. A cav-1 inhibitor abrogated the effect of bFGF on cell viability. The expression levels of bFGF mRNA, bFGF protein, cav-1 mRNA, cav-1 protein, and VEGF protein were higher in OGD/R astrocytes. bFGF knockdown markedly decreased the expression levels of cav-1 mRNA, cav-1 protein, and VEGF protein, which were effectively reversed by exogenous bFGF treatment. Moreover, exogenous bFGF treatment significantly increased the expression levels of cav-1 mRNA, cav-1 protein, and VEGF protein in OGD/R astrocytes; however, a cav-1 inhibitor abolished the effect of bFGF on VEGF protein expression. These results suggested that bFGF may protect astrocytes against ischemia/reperfusion injury by upregulating caveolin-1/VEGF signaling pathway.

The aPKC-CBP Pathway Regulates Post-stroke Neurovascular Remodeling and Functional Recovery

Epigenetic modifications have emerged as attractive molecular substrates that integrate extrinsic changes into the determination of cell identity. Since stroke-related brain damage releases micro-environmental cues, we examined the role of a signaling-induced epigenetic pathway, an atypical protein kinase C (aPKC)-mediated phosphorylation of CREB-binding protein (CBP), in post-stroke neurovascular remodeling. Using a knockin mouse strain (CbpS436A) where the aPKC-CBP pathway was defective, we show that disruption of the aPKC-CBP pathway in a murine focal ischemic stroke model increases the reprogramming efficiency of ischemia-activated pericytes (i-pericytes) to neural precursors. As a consequence of enhanced cellular reprogramming, CbpS436A mice show an increased transient population of locally derived neural precursors after stroke, while displaying a reduced number of i-pericytes, impaired vascular remodeling, and perturbed motor recovery during the chronic phase of stroke. Together, this study elucidates the role of the aPKC-CBP pathway in modulating neurovascular remodeling and functional recovery following focal ischemic stroke.

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CbpS436A increases the reprogramming efficiency of i-pericytes to NPCs in culture

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CbpS436A increases the number of locally derived NPCs from i-pericyte in vivo

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CbpS436A shows impaired vascular remodeling and functional recovery after stroke

Transplantation of bFGF-expressing neural stem cells promotes cell migration and functional recovery in rat brain after transient ischemic stroke

Cerebrovascular disease such as stroke is one of the most common diseases in the aging population, and neural stem cells (NSCs) transplantation may provide an alternative therapy for cerebral ischemia. However, a hostile microenvironment in the ischemic brain offers is challenging for the survival of the transplanted cells. Considering the neuroprotective role of basic fibroblast growth factor (bFGF), the present study investigated whether bFGF gene-modified NSCs could improve the neurological function deficit after transient middle cerebral artery occlusion (MCAO) in adult male Sprague-Dawley rats. These rats were intravenously injected with modified NSCs (5×10⁶/200 μL) or vehicle 24 h after MCAO. Histological analysis was performed on days 7 and 28 after tMCAO. The survival, migration, proliferation, and differentiation of the transplanted modified C17.2 cells in the brain were improved. In addition, the intravenous infusion of NSCs and bFGF gene-modified C17.2 cells improved the functional recovery as compared to the control. Furthermore, bFGF promoted the C17.2 cell growth, survival, and differentiation into mature neurons within the infarct region. These data suggested that bFGF gene-modified NSCs have the potential to be a therapeutic agent in brain ischemia.

Cerebrolysin for functional recovery in patients with acute ischemic stroke: a meta-analysis of randomized controlled trials

Cerebrolysin has been shown to have an inconsistent efficacy on functional recovery in patients with acute ischemic stroke (AIS). The present meta-analysis aims to evaluate the value of cerebrolysin and to explore the potential influencing factors. The main electronic databases, including MEDLINE, EMBASE, and the Cochrane Library, were searched. The primary outcome was functional recovery at Day 90. The secondary outcomes included mortality and adverse events. A total of 1,649 patients with AIS were pooled from six randomized controlled trials (RCTs). Cerebrolysin had no significant effect on functional recovery at Day 90 compared with the effect of placebo as shown by the modified Rankin Scale response (relative risk [RR] 1.33, 95% confidence interval [CI] 0.79–2.24, P=0.28), National Institutes of Health Stroke Scale response (RR 1.03, 95% CI 0.83–1.28, P=0.77), and Barthel Index response (RR 0.95, 95% CI 0.84–1.08, P=0.44). In safety analysis, cerebrolysin did not increase the risk of adverse events (RR 0.98, 95% CI 0.88–1.09, P=0.67), risk of serious adverse events (RR 1.20, 95% CI 0.86–1.66, P=0.29), or the mortality rate (RR 0.86, 95% CI 0.57–1.31, P=0.49). In conclusion, routine administration of cerebrolysin to patients with AIS cannot be supported by the available evidence from RCTs.

Paracrine Mechanisms of Intravenous Bone Marrow-Derived Mononuclear Stem Cells in Chronic Ischemic Stroke

Background

The emerging role of stem cell technology and transplantation has helped scientists to study their potential role in neural repair and regeneration. The fate of stem cells is determined by their niche, consisting of surrounding cells and the secreted trophic growth factors. This interim report evaluates the safety, feasibility and efficacy (if any) of bone marrow-derived mononuclear stem cells (BM-MNC) in chronic ischemic stroke by studying the release of serum vascular endothelial growth factor (VEGF) and brain-derived neurotrophic growth factor (BDNF).

Methods

Twenty stroke patients and 20 age-matched healthy controls were recruited with the following inclusion criteria: 3 months to 1.5 years from the index event, Medical Research Council (MRC) grade of hand muscles of at least 2, Brunnstrom stage 2-5, conscious, and comprehendible. They were randomized to one group receiving autologous BM-MNC (mean 60-70 million) and to another group receiving saline infusion (placebo). All patients were administered a neuromotor rehabilitation regime for 8 weeks. Clinical assessments [Fugl Meyer scale (FM), modified Barthel index (mBI), MRC grade, Ashworth tone scale] were carried out and serum VEGF and BDNF levels were assessed at baseline and at 8 weeks.

Results

No serious adverse events were observed during the study. There was no statistically significant clinical improvement between the groups (FM: 95% CI 15.2-5.35, p = 0.25; mBI: 95% CI 14.3-4.5, p = 0.31). VEGF and BDNF expression was found to be greater in group 1 compared to group 2 (VEGF: 442.1 vs. 400.3 pg/ml, p = 0.67; BDNF: 21.3 vs. 19.5 ng/ml) without any statistically significant difference.

Conclusion

Autologous mononuclear stem cell infusion is safe and tolerable by chronic ischemic stroke patients. The released growth factors (VEGF and BDNF) in the microenvironment could be due to the paracrine hypothesis of stem cell niche and neurorehabilitation regime.

Regulation of Dipeptidyl Peptidase IV in the Post-stroke Rat Brain and In Vitro Ischemia: Implications for Chemokine-Mediated Neural Progenitor Cell Migration and Angiogenesis

Cerebral ischemia evokes abnormal release of proteases in the brain microenvironment that spatiotemporally impact angio-neurogenesis. Dipeptidyl peptidase IV (DPPIV), a cell surface and secreted protease, has been implicated in extracellular matrix remodeling by regulating cell adhesion, migration, and angiogenesis through modifying the functions of the major chemokine stromal-derived factor, SDF1. To elucidate the possible association of DPPIV in ischemic brain, we examined the expression of DPPIV in the post-stroke rat brain and under in vitro ischemia by oxygen glucose deprivation (OGD). We further investigated the effects of DPPIV on SDF1 mediated in vitro chemotactic and angiogenic functions. DPPIV protein and mRNA levels were significantly upregulated during repair phase in the ischemic cortex of the rat brain, specifically in neurons, astrocytes, and endothelial cells. In vitro exposure of Neuro-2a neuronal cells and rat brain endothelial cells to OGD resulted in upregulation of DPPIV. In vitro functional analysis showed that DPPIV decreases the SDF1-mediated angiogenic potential of rat brain endothelial cells and inhibits the migration of Neuro-2a and neural progenitor cells. Western blot analyses revealed decreased levels of phosphorylated ERK1/2 and AKT in the presence of DPPIV. DPPIV inhibitor restored the effects of SDF1. Proteome profile array screening further revealed that DPPIV decreases matrix metalloproteinase-9, a key downstream effector of ERK-AKT signaling pathways. Overall, delayed induction of DPPIV in response to ischemia/reperfusion suggests that DPPIV may play an important role in endogenous brain tissue remodeling and repair processes. This may be mediated through modulation of SDF1-mediated cell migration and angiogenesis.

Intraventricular infusion of a low fraction of serum enhances neurogenesis and improves recovery in a rodent stroke model

Enhancing endogenous neurogenesis is a potential therapeutic strategy in stroke treatment. We have previously demonstrated that treatment with a fraction of serum with molecular weight of less than 100 kDa (100K) combined with bFGF promoted neurogenesis of cultured stem and progenitor cells (NSPCs). In this study, we further evaluated the efficacy of intraventricular administration of 100K with bFGF (100K/bFGF) in a rat model of transient middle cerebral artery occlusion (MCAO). Rats administered 100K/bFGF on post-stroke day 1 exhibited a higher number of Ki67 and Nestin immunoreactive cells at the subventricular zone (SVZ) area and in the infarcted brain, indicating promotion of NSPCs proliferation. The 100K/bFGF treatment also predominantly increased the number of MAP-2 immunoreactive cells rather than GFAP immunoreactive cells at the SVZ area and in the infarcted regions, implying that 100K/bFGF dominated NSPCs differentiating into neurons rather than astrocytes. Importantly, treatment with 100K/bFGF significantly improved the animals' motor coordination. These findings demonstrated that treatment with a low serum fraction and bFGF benefited ischemic stroke likely through promotion of the proliferation and neuronal differentiation of endogenous NSPCs.

Neuroprotective effects of SMADs in a rat model of cerebral ischemia/reperfusion

Previous studies have shown that up-regulation of transforming growth factor β1 results in neuroprotective effects. However, the role of the transforming growth factor β1 downstream molecule, SMAD2/3, following ischemia/reperfusion remains unclear. Here, we investigated the neuroprotective effects of SMAD2/3 by analyzing the relationships between SMAD2/3 expression and cell apoptosis and inflammation in the brain of a rat model of cerebral ischemia/reperfusion. Levels of SMAD2/3 mRNA were up-regulated in the ischemic penumbra 6 hours after cerebral ischemia/reperfusion, reached a peak after 72 hours and were then decreased at 7 days. Phosphorylated SMAD2/3 protein levels at the aforementioned time points were consistent with the mRNA levels. Over-expression of SMAD3 in the brains of the ischemia/reperfusion model rats via delivery of an adeno-associated virus containing the SMAD3 gene could reduce tumor necrosis factor-α and interleukin-1β mRNA levels, down-regulate expression of the pro-apoptotic gene, capase-3, and up-regulate expression of the anti-apoptotic protein, Bcl-2. The SMAD3 protein level was negatively correlated with cell apoptosis. These findings indicate that SMAD3 exhibits neuroprotective effects on the brain after ischemia/reperfusion through anti-inflammatory and anti-apoptotic pathways.

Stem cell transplantation for treating stroke: status, trends and development

The developing approaches of thrombolytic therapy, endovascular treatment, neuroprotective therapy, and stem cell therapy have enabled breakthroughs in stroke treatment. In this study, we summarize and analyze trends and progress in stem cell transplantation for stroke treatment by retrieval of literature from Thomson Reuters Web of Science database, the NIH Clinical Trial Planning Grant Program, and Clinical Trials Registration Center in North America. In the last 10 years, there has been an increasing number of published articles on stem cell transplantation for stroke treatment. In particular, research from the USA and China has focused on stem cell transplantation. A total of 2,167 articles addressing stem cell transplantation for stroke treatment from 2004 to 2013 were retrieved from the Thomson Reuters Web of Science database. The majority of these articles were from the USA (854, 39.4%), with the journal Stroke publishing the most articles (145, 6.7%). Of the published articles, 143 were funded by the National Institutes of Health (accounting for 6.6% of total publications), and 91 by the National Natural Science Foundation of China. Between 2013 and 2014, the National Institutes of Health provided financial support ($130 million subsidy) for 329 research projects on stroke therapy using stem cell transplantation. In 2014, 215 new projects were approved, receiving grants of up to $70,440,000. Ninety clinical trials focusing on stem cell transplantation for stroke were registered in the Clinical Trial Registration Center in North America, with 40 trials registered in the USA (ranked first place). China had the maximum number of registered research or clinical trials (10 projects).

Mesenchymal stem cells expressing brain-derived neurotrophic factor enhance endogenous neurogenesis in an ischemic stroke model

Numerous studies have reported that mesenchymal stem cells (MSCs) can ameliorate neurological deficits in ischemic stroke models. Among the various hypotheses that have been suggested to explain the therapeutic mechanism underlying these observations, neurogenesis is thought to be critical. To enhance the therapeutic benefits of human bone marrow-derived MSCs (hBM-MSCs), we efficiently modified hBM-MSCs by introduction of the brain-derived neurotrophic factor (BDNF) gene via adenoviral transduction mediated by cell-permeable peptides and investigated whether BDNF-modified hBM-MSCs (MSCs-BDNF) contributed to functional recovery and endogenous neurogenesis in a rat model of middle cerebral artery occlusion (MCAO). Transplantation of MSCs induced the proliferation of 5-bromo-2′-deoxyuridine (BrdU-) positive cells in the subventricular zone. Transplantation of MSCs-BDNF enhanced the proliferation of endogenous neural stem cells more significantly, while suppressing cell death. Newborn cells differentiated into doublecortin (DCX-) positive neuroblasts and Neuronal Nuclei (NeuN-) positive mature neurons in the subventricular zone and ischemic boundary at higher rates in animals with MSCs-BDNF compared with treatment using solely phosphate buffered saline (PBS) or MSCs. Triphenyltetrazolium chloride staining and behavioral analysis revealed greater functional recovery in animals with MSCs-BDNF compared with the other groups. MSCs-BDNF exhibited effective therapeutic potential by protecting cell from apoptotic death and enhancing endogenous neurogenesis.

Safety and efficient ex vivo expansion of stem cells using platelet-rich plasma technology

The goal of this Review is to provide an overview of the cell culture media supplements used in the ex vivo expansion of stem cells intended for cell therapy. Currently, the gold standard is the culture supplemented with fetal bovine serum, however, their use in cell therapy raises many concerns. The alternatives to its use are presented, ranging from the use of human serum to platelet-rich plasma (PRP), to serum-free media or extracellular matrix components. Finally, various growth factors present in PRP are described, which make it a safe and effective stem cell expansion supplement. These growth factors could be responsible for their efficiency, as they increase both stem cell proliferation and survival. The different PRP formulations are also discussed, as well as the need for protocol standardization.

Modulation of neural stem/progenitor cell proliferation during experimental Herpes Simplex encephalitis is mediated by differential FGF-2 expression in the adult brain

Neural stem cells (NSCs) respond to inflammatory cues induced during brain injury and are thought to be involved in recovery from brain damage. Little is known about NSC response during brain infections. The present study evaluated NSC proliferation during Herpes Simplex Virus-1 brain infection. Total numbers of nestin(+) NSCs increased significantly in infected brains at 6 days post infection (p.i.). However, by 15 days p.i. the nestin(+) population decreased significantly below levels observed in uninfected brains and remained depressed through 30 days p.i. This initial increase in NSC population occurred concurrently with increased brain cell proliferation, which peaked at 3 days p.i. On closer examination, we found that while actively proliferating Sox2(+) NSCs increased in number at 6 days p.i., proliferating DCX(+) neuroblasts contributed to the increased response at 3 days p.i. However, overall proliferation decreased steadily from 15 days p.i. to below control levels. To determine the mechanisms involved in altering NSC proliferation, neurotrophin and growth factor expression profiles were assessed. FGF-2 gene expression increased at 5 days p.i. and was robustly down-regulated at 15 days p.i. (>1000-fold), which was further confirmed by increased FGF-2 immunostaining around the lateral ventricles. Furthermore, supplementing infected animals with recombinant FGF-2, at 15 days p.i., significantly increased the number of proliferating brain cells. These findings demonstrate that the temporal changes in NSC proliferation are mediated through the regulation of FGF-2 and that the NSC niche may benefit from supplementation with FGF-2 during HSV-1 brain infection.

A hydrogel composite system for sustained epi-cortical delivery of Cyclosporin A to the brain for treatment of stroke

Stimulation of endogenous neural stem/progenitor cells (NSPCs) with therapeutic factors holds potential for the treatment of stroke. Cyclosporin A (CsA) is a particularly promising candidate molecule because it has been shown to act as a survival factor for these cells over a period of weeks both in vitro and in vivo; however, systemically-delivered CsA compromises the entire immune system, necessitating sustained localized delivery. Herein we describe a local delivery strategy for CsA using an epi-cortical hydrogel of hyaluronan-methylcellulose (HAMC) as the drug reservoir. Three methods of incorporating the drug into the hydrogel (solubilized, particulate, and poly(lactic-co-glycolic) acid (PLGA) microsphere-encapsulated) resulted in tunable release, spanning a period of hours to weeks. Importantly, PLGA-encapsulated CsA released from the hydrogel had equivalent bioactivity to fresh drug as measured by the neurosphere assay. Moreover, when CsA was released from the PLGA/HAMC composite that was injected on the cortex of adult mice, CsA was detected in the NSPC niche at a constant concentration for at least 24days post-implant. Thus this hydrogel composite system may be promising for the treatment of stroke.

Role of neural precursor cells in promoting repair following stroke

Stem cell-based therapies for the treatment of stroke have received considerable attention. Two broad approaches to stem cell-based therapies have been taken: the transplantation of exogenous stem cells, and the activation of endogenous neural stem and progenitor cells (together termed neural precursors). Studies examining the transplantation of exogenous cells have demonstrated that neural stem and progenitor cells lead to the most clinically promising results. Endogenous activation of neural precursors has also been explored based on the fact that resident precursor cells have the inherent capacity to proliferate, migrate and differentiate into mature neurons in the uninjured adult brain. Studies have revealed that these neural precursor cell behaviours can be activated following stroke, whereby neural precursors will expand in number, migrate to the infarct site and differentiate into neurons. However, this innate response is insufficient to lead to functional recovery, making it necessary to enhance the activation of endogenous precursors to promote tissue repair and functional recovery. Herein we will discuss the current state of the stem cell-based approaches with a focus on endogenous repair to treat the stroke injured brain.

Galectin-3 enhances angiogenic and migratory potential of microglial cells via modulation of integrin linked kinase signaling

Focal cerebral ischemia initiates self-repair mechanisms that include the production of neurotrophic factors and cytokines. Galectin-3 is an important angiogenic cytokine. We have previously demonstrated that expression of galectin 3 (Gal-3), a carbohydrate binding protein is significantly upregulated in activated microglia in the brains of rats subjected to focal ischemia. Further blocking of Gal-3 function with Gal-3 neutralizing antibody decreased the microvessel density in ischemic brain. We currently show that Gal-3 significantly increases the viability of microglia BV2 cells subjected to oxygen glucose deprivation (OGD) and re-oxygenation. Exogenous Gal-3 promoted the formation of pro-angiogenic structures in an in vitro human umbilical vein endothelial (HUVEC) and BV2 cell co-culture model. Gal-3 induced angiogenesis was associated with increased expression of vascular endothelial growth factor. The conditioned medium of BV2 cells exposed to OGD contained increased Gal-3 levels, and promoted the formation of pro-angiogenic structures in an in vitro HUVEC culture model. Gal-3 also augmented the in vitro migratory potential of BV2 microglia. Gal-3 mediated functions were associated with increased levels of integrin-linked kinase (ILK) signaling as demonstrated by the impaired angiogenesis and migration of BV2 cells following targeted silencing of ILK expression by siRNA. Furthermore, we show that ILK levels correlate with the levels of phos-AKT and ERK1/2 that are downstream effectors of ILK pathway. Taken together, our studies indicate that Gal-3 contributes to angiogenesis and microglia migration that may have implications in post stroke repair.

A prospective, randomized, placebo-controlled, double-blind trial about safety and efficacy of combined treatment with alteplase (rt-PA) and Cerebrolysin in acute ischaemic hemispheric stroke

BACKGROUND

The neurotrophic drug Cerebrolysin accelerated recovery and prevented acute neuronal damage in preclinical models of ischaemia. Previous clinical trials support therapeutic effects in stroke patients. The study investigated whether the combination with alteplase and Cerebrolysin is safe and can further reduce disability after acute ischaemic stroke.

METHODS

This placebo-controlled, double-blind trial involved 119 patients with acute ischaemic hemispheric stroke, randomly assigned to a combined treatment with alteplase plus Cerebrolysin or placebo (administered 1 h after thrombolytic treatment) starting within three-hours after onset of symptoms. A daily i.v. infusion of 30 ml Cerebrolysin or placebo was given for 10 consecutive days. Primary outcome was the modified Rankin Scale at day 90. A sequential design with interim analyses was applied.

RESULTS

The third interim analysis did not show a benefit in the modified Rankin Scale for Cerebrolysin on day 90 compared to placebo and the study was stopped. The National Institutes of Health Stroke Scale responder analysis (secondary outcome measure) showed significantly more patients with an improvement of 6 or more points (or a total score of 0 or 1) after two-, five-, 10, and 30 days in the Cerebrolysin group. Similar trends were observed for the modified Rankin Scale responder analysis without achieving statistical significance. There was no difference between treatment groups regarding adverse events.

CONCLUSIONS

The combination of Cerebrolysin with recombinant tissue-Plasminogen Activator is safe for treatment of acute ischaemic stroke but did not improve outcome at day 90. During the treatment period with Cerebrolysin (10 days), significantly more patients had a favourable response in neurological outcome measures (National Institutes of Health Stroke Scale) as compared to the placebo group.

Identification of a neuronal gene expression signature: role of cell cycle arrest in murine neuronal differentiation in vitro

Stem cells are a potential key strategy for treating neurodegenerative diseases in which the generation of new neurons is critical. A better understanding of the characteristics and molecular properties of neural stem cells (NSCs) and differentiated neurons can help with assessing neuronal maturity and, possibly, in devising better therapeutic strategies. We have performed an in-depth gene expression profiling study of murine NSCs and primary neurons derived from embryonic mouse brains. Microarray analysis revealed a neuron-specific gene expression signature that distinguishes primary neurons from NSCs, with elevated levels of transcripts involved in neuronal functions, such as neurite development and axon guidance in primary neurons and decreased levels of multiple cytokine transcripts. Among the differentially expressed genes, we found a statistically significant enrichment of genes in the ephrin, neurotrophin, CDK5, and actin pathways, which control multiple neuronal-specific functions. We then artificially blocked the cell cycle of NSCs with mitomycin C (MMC) and examined cellular morphology and gene expression signatures. Although these MMC-treated NSCs displayed a neuronal morphology and expressed some neuronal differentiation marker genes, their gene expression patterns were very different from primary neurons. We conclude that 1) fully differentiated mouse primary neurons display a specific neuronal gene expression signature; 2) cell cycle block at the S phase in NSCs with MMC does not induce the formation of fully differentiated neurons; 3) cytokines change their expression pattern during differentiation of NSCs into neurons; and 4) signaling pathways of ephrin, neurotrophin, CDK5, and actin, related to major neuronal features, are dynamically enriched in genes showing changes in expression level.

Growth hormone and prolactin regulate human neural stem cell regenerative activity

We have previously shown that the growth hormone (GH)/prolactin (PRL) axis has a significant role in regulating neuroprotective and/or neurorestorative mechanisms in the brain and that these effects are mediated, at least partly, via actions on neural stem cells (NSCs). Here, using NSCs with properties of neurogenic radial glia derived from fetal human forebrains, we show that exogenously applied GH and PRL promote the proliferation of NSCs in the absence of epidermal growth factor or basic fibroblast growth factor. When applied to differentiating NSCs, they both induce neuronal progenitor proliferation, but only PRL has proliferative effects on glial progenitors. Both GH and PRL also promote NSC migration, particularly at higher concentrations. Since human GH activates both GH and PRL receptors, we hypothesized that at least some of these effects may be mediated via the latter. Migration studies using receptor-specific antagonists confirmed that GH signals via the PRL receptor promote migration. Mechanisms of receptor signaling in NSC proliferation, however, remain to be elucidated. In summary, GH and PRL have complex stimulatory and modulatory effects on NSC activity and as such may have a role in injury-related recovery processes in the brain.

Mesenchymal stem cells increase hippocampal neurogenesis and counteract depressive-like behavior

Adult bone marrow-derived mesenchymal stem cells (MSCs) are regarded as potential candidates for treatment of neurodegenerative disorders, because of their ability to promote neurogenesis. MSCs promote neurogenesis by differentiating into neural lineages as well as by expressing neurotrophic factors that enhance the survival and differentiation of neural progenitor cells. Depression has been associated with impaired neurogenesis in the hippocampus and dentate gyrus. Therefore, the aim of this study was to analyze the therapeutic potential of MSCs in the Flinders sensitive line (FSL), a rat animal model for depression. Rats received an intracerebroventricular injection of culture-expanded and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled bone marrow-derived MSCs (10⁵ cells). MSC-transplanted FSL rats showed significant improvement in their behavioral performance, as measured by the forced swim test and the dominant-submissive relationship (DSR) paradigm. After transplantation, MSCs migrated mainly to the ipsilateral dentate gyrus, CA1 and CA3 regions of the hippocampus, and to a lesser extent to the thalamus, hypothalamus, cortex and contralateral hippocampus. Neurogenesis was increased in the ipsilateral dentate gyrus and hippocampus of engrafted rats (granular cell layer) and was correlated with MSC engraftment and behavioral performance. We therefore postulate that MSCs may serve as a novel modality for treating depressive disorders.

Stroke rehabilitation: strategies to enhance motor recovery

Recent evidence indicates that the brain can remodel after stroke, primarily through synaptogenesis. Task-specific and repetitive exercise appear to be key factors in promoting synaptogenesis and are central elements in rehabilitation of motor weakness following stroke. Expert medical management ensures a patient is well enough to participate in rehabilitation with minimal distractions due to pain or depression. Contraint-induced motor therapy and body-weight-supported ambulation are forms of exercise that "force use" of an impaired upper extremity. Technologies now in common use include robotics, functional electrical stimulation, and, to a lesser degree, transcranial magnetic stimulation and virtual reality. The data on pharmacological interventions are mixed but encouraging; it is hoped such treatments will directly stimulate brain tissue to recovery. Mitigation of factors preventing movement, such as spasticity, might also play a role. Research evaluating these motor recovery strategies finds them generally good at the movement level but somewhat less robust when looking at functional performance. It remains unclear whether inconsistent evidence for functional improvement is a matter of poor treatment efficacy or insensitive outcome measures.

Introduction of hIGF-1 gene into bone marrow stromal cells and its effects on the cell's biological behaviors

Autologous and gene-modified bone marrow stromal cells (MSCs) have shown a bright future in clinical applications. However, does a gene-modified MSC still maintain its stem cell-like properties? To answer this question, human IGF-1 was introduced into rat MSCs using a recombinant retroviral vector and the effects of the gene manipulation on the cells' behaviors were investigated. The MSCs transfected with hIGF-1 could secrete 6.7-fold higher IGF-1 than the native cells. These MSCs had an elevated baseline activity of ERK signaling, an enhanced proliferation, increased accumulative numbers of cell doublings, and a reduced apoptosis; they showed upregulated expressions of OCT-4, CYP51, and SM22alpha, and a downregulated expression of nestin. This indicates that the overexpressed IGF-1 enhances the MSCs' self-renewal, endodermal and mesodermal differentiation, but weakens their neuronal potential. Although a puromycin selection after hIGF-1 gene transfection could produce a purer transfected MSC population with stronger ability to express functional hIGF-1, it induced premature senescence of the selected cells by activating oncogene Ras, leading to a shortened replicative life span and a weakened multipotency.

The potential of neural stem cells to repair stroke-induced brain damage

Acute injuries to CNS such as stroke induce neural progenitor proliferation in adult brain which might be an endogenous attempt to self-repair. This process is known to be altered by several exogenous and endogenous modulators including growth factors that could help to reinforce the post-stroke neurogenesis. Increasing the neurogenesis may be a future therapeutic option to decrease the cognitive and behavioral deficits following stroke. In addition, transplantation of various types of stem cells into the injured brain is currently thought to be an exciting option to replace the neurons lost in the post-ischemic brain. These include immortalized stem cell lines, neural progenitors prepared from embryonic and adult animals and mesenchymal stem cells. Using exogenous stem cells in addition to modulating endogenous neurogenesis, we may be able to repair the injured brain after a devastating stroke. This article reviewed the current literature of these two issues.

The physiological basis of intracrine stem cell regulation

Intracrine peptides and proteins participate in the regulation of adult and pleuripotential embryonic-like stem cells. Included among these factors are VEGF, dynorphin, the readthrough form of acetylcholinesterase, Oct3/4, Pdx-1, Pax-6, and high-mobility group protein B1, among others. In some cases, the establishment of intracrine feedback loops can be shown to be relevant to this regulation, consistent with previously proposed principles of intracrine action. Here the role of intracrines in stem cell regulation is reviewed, with particular attention to the intracrine regulation of cardiac stem cells. The reprogramming of cells to restore the pleuripotent phenotype and the possible role of stem/progenitor cells in neoplasia are also discussed.